Greg and Karin head into the field to practice their rock reading skills on a beach in Tasmania.
Summary
- If we assume that the same processes operated in the past as now operate then we can read the rocks. This is the principle of uniformitarianism.
- Sediments are laid down, one on top of the other in sub-horizontal layers.
- In sedimentary rocks, the oldest rocks are at the bottom and get younger as you go up unless the rocks have later been turned over by folding or some other mechanism.
- Fossils can be preserved in sedimentary rocks and, because they are the same age, they can help us work out how old the rocks are.
- The size of grains in sedimentary rocks tell us about the environment in which they were laid down – small grains means that the sediments were laid down in calmer waters than large grains.
- Some special features tell us more – like dropstones as evidence of icebergs (and therefore cold climates).
- Features that cross-cut sedimentary rocks must have been formed after the sediments had turned to rock.
- Rocks formed from magma (molten rock) often cross cut sedimentary rocks, and represent the intrusion of the magma in dykes through the sedimentary rocks.
- The crystal size in igneous rocks (those formed from magma) tell us about conditions – small crystals indicate that the magma solidified quickly (for example basalt that solidified on or near the earth’s surface); large crystals occur in rocks that solidified deep in the earth.
- This is just the beginning, if you look in more detail, then you can work out much more from rocks.
Rock Reading, it's all in the detail.
This quiz consists of 4 questions. The questions are about information on reading rocks. This task is to help you review the main ideas in the video and reading the rock section and help you prepare a bit for your own field trip in assessment task 1a.
Greg and Karin head into the field to practice their rock reading skills on a beach in Tasmania.
Summary
Rock Reading, it's all in the detail.
This quiz consists of 4 questions. The questions are about information on reading rocks. This task is to help you review the main ideas in the video and reading the rock section and help you prepare a bit for your own field trip in assessment task 1a.
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